Ultrathin gate SiOxNy (y similar to 0.3-0.4%) films between 1 and 2 nm were grown in a vertical batch fast thermal processing system. Leakage currents were monitored as a function of film thickness (T), purge gas, oxidation ambient, and different annealing conditions. Ultrathin oxynitrides down to 1.2 nm with leakage < 1A/cm(2) have been fabricated. Of the different purge gases studied, O-2 purge gave the highest leakage, while the trend indicated that NO purge would give the lowest leakage for T-ox < 1.5 nm. Similarly, while oxidation with O-2 yielded the poorest leakage, the trend indicated that NO oxide would give a much lower leakage for T-ox < 1.5 nm. The effect of the process conditions on the metal oxide semiconductor transistor mobility was also examined. The high field mobility has a stronger dependence on the process temperature than on process ambient.